Modelling and evaluation of mean time to repair at product design stage based on contextual criteria

Abstract

Time to repair of a mechanical system is a function of its maintainability and external influences in the plant. Repairability means the ease of maintenance. In this paper, repairability features of the mechanical system are identified, and are modelled in terms of repairability digraph. The nodes in the digraph represent the repairability features and the edges represent the degree of influence among these. An equivalent matrix representation of the digraph is developed to define the system repairability function (SRF). Repairability correction factor (RCF) is defined as a ratio of the actual to the ideal values of SRF. A high value of RCF indicates that the system support structure is closer to the ideal state, which implies that the mean time to repair (MTTR) is same as that estimated by the designer. The presented model is illustrated with an example. The results show that the MTTR of mechanical equipment, based on contextual criteria, can be predicted, by extrapolating the design value of MTTR. The proposed methodology is capable of evaluating the realistic MTTR based on plant influencing factors and is expected to aid the designers in selecting the best design and will also help the maintenance planners.

Keywords:

• repairability
• maintainability
• service-design
• contextual parameters
• digraph model

Acknowledgements

The authors thank the reviewers and the editor for their valuable comments and suggestions.